1. Field of the Invention
The present invention relates to a method of manufacturing a tire, and an apparatus for manufacturing a green tire. In particular, it relates to a method of manufacturing a tire whereby tire structural members such as a carcass, a bead core, a belt, and a tread are provided around a toroidal hard core to form a green tire, and the green tire is loaded in a mold, together with the hard core, and vulcanized to obtain a pneumatic tire; and to an apparatus for manufacturing a green tire applicable to the method of manufacturing a tire.
2. Description of the Related Art
There are two types of methods of forming a pneumatic tire: one of putting a green tire, formed in a tire-molding drum, into a mold, inflating it with a bladder, and vulcanizing the green tire; and the other of forming a green tire on an external surface of a metal hard core formed in a toroidal shape, putting the green tire in a mold with the hard core, and vulcanizing the green tire (a “core manufacturing method”).
When a green tire is formed within a tire-molding drum, ordinarily, as shown in FIG. 14, edge portions of a carcass ply 100 are turned up from inside bead cores 102 to the outside thereof (a “turn-up structure”).
In the core manufacturing method, tire structural members are set on an external surface of the hard core in the order of an inner liner, a carcass ply, and bead cores. As shown in FIG. 15, bead portions according to a conventional core manufacturing method are mainly of a type in which edge portions of the carcass ply 100 are sandwiched between two plate-shaped bead cores 104 and 106, which are formed in a toroidal shape. As shown in FIG. 16, there is also provided another type in which edge portions of the carcass ply 100 are bent toward the outside of bead cores 102 (a kind of a “turn-up structure”).
However, among tires manufactured in accordance with conventional core manufacturing methods, no tire having bead portions with the kind of turn-up structure shown in FIG. 14 has been available on the commercial market. This is because facilities for literally “turning up” carcass plies have not been proposed as facilities for tire manufacturing according to the core manufacturing method.
Tires having bead portions of the types shown in FIGS. 15 and 16 have low general rigidity, and, in particular, low transverse rigidity. Further, a problem is caused in that tuning-up of a tire by turning up bead portions thereof cannot be conducted in the tires having bead portions of the types shown in FIGS. 15 and 16, which would be possible in the tire having bead portions of the types shown in FIG. 14.
The present invention has been devised in order to solve the aforementioned problems. Therefore, an object of the present invention is to provide, in accordance with the core manufacturing method, a method of manufacturing a tire in which edge portions of a carcass ply can be turned up at bead cores and an apparatus for manufacturing a green tire applicable to the method of manufacturing a tire.